ANIMAL LIFE IN PONDS & STREAMS 



is impossible to describe all the interesting creatures 

 we might find : we must content ourselves with two, 

 because they are common inhabitants of many 

 ponds. One interesting little creature we are almost 

 certain to find, the Hydra, He may be green or 

 he may be brown but in structure he will remind us 

 of a small sea anemone. When we put him under 

 the microscope he has the apperance of a mass of 

 jelly attached to the water plant on which we found 

 him. He will soon open himself out, however, and 

 we shall see that his free end is provided with a 

 number of tentacles; these he waves about in the 

 water to draw small swimming creatures to his 

 mouth which is situated in the centre of the group 

 of tentacles. Any luckless creature, coming within 

 reach of the Hydra, is at once stung with one of the 

 barb-shaped stings which stud his tentacles and then 

 passed to his mouth. The Hydra is wonderfully 

 tenacious of life; it is said that he has been turned 

 inside out, like a glove finger, without suffering any 

 inconvenience. Probably the specimen we are ex- 

 amining will have a swelling on the side of its body, 

 which might be mistaken for the result of some 

 injury; it is nothing of the kind; it is merely a 

 bud which will grow into a young Hydra and, when 

 old enough, become detached from its parent and 

 float away to another plant. Under a fairly high 

 magnification, we shall almost certainly see some- 

 thing gliding rapidly over the body of the Hydra; 

 its movements are too quick to allow of careful 

 examination ; the creature which is almost as elusive 



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